The present invention relates to a system for detecting crank angle of a two-cycle engine.
In order to economize fuel consumption and to improve performance of the two-cycle engine as well as an emission control, a fuel injection timing and an ignition timing of the engine are controlled by an electronic control system. In the electronic control system, the crank angle is detected for controlling the fuel injection timing and the ignition timing.
Japanese Utility Model Application Laid-open 59-109914 discloses a crank angle detecting system in which a rotating disk having a plurality of slits and reflecting plates is secured to a crankshaft of the engine. The slits and reflecting plates are provided on the rotating disk at predetermined distances for detecting the crank angle and for discriminating a cylinder number, respectively. The crank angle is detected by lights which are emitted from a light emitting device passing through the slits. The lights reflected on the reflecting plates are detected by a photo detector for discriminating the cylinder number.
Japanese Utility Model Application Laid-open 59-174335 discloses a rotating angle sensor in which a plurality of projections made of magnetic material are provided on a rotor plate in place of the reflecting plates. The projections are detected by a magnetic detecting device for discriminating the cylinder number.
In the two-cycle engine, it is desirable to provide a crank angle detecting system having functions as follows:
(1) producing pulses as a basic signal for controlling the fuel injection and ignition,
(2) discriminating the cylinder number,
(3) determining the rotating direction of the crankshaft, for preventing rotation in the reverse direction,
(4) determining fixed timings for fuel injection and ignition at starting of the engine.
If the crank angle detecting system has the above four functions, it is possible to simplify the electronic control, thereby improving control accuracy.
However, in the conventional devices, since the function relative to the rotating direction and the fixed timings for the fuel injection and ignition at starting are not provided in the crank angle detecting system, it is impossible to simplify the control and to improve the control accuracy.